Nutrient and phytoplankton dynamics in a sewage-impacted Gulf coast estuary: A field test of the PEG-model and equilibrium resource competition theory

Eutrophication and noxious bloom events are becoming more prevalent with increasing anthropogenic activities. To lessen ecological damage, there is a need to develop phytoplankton management programs aimed at enhancing growth of beneficial algae. The success of such management schemes with be dependent on the predictability of phytoplankton succession within the target system to a controlled perturbation. Freshwater lakes appear to exhibit a degree of predictability as described by the PEG-model and Equilibrium Resource Competition theory. We investigated whether these concepts could be applied to a marine system, the Nueces River estuary, Texas. The PEG-model predicted nicely the initial occurrence of edible phytoplankton forms after a favorable nutrient perturbation. Equilibrium Resource Competition theory, however, only successfully predicted the occurrence of major phytoplankton taxa immediately after a nutrient perturbation. Systemwide correlations between N:P and cyanobacteria, green algae, and diatoms were poor. In the Nueces River estuary, succession within the phytoplankton community showed a degree of predictability to nutrient perturbations. Therefore, management of the phytoplankton community composition may be possible. The PEG-model appears to be a useful guide for a phytoplankton management scheme, while the utility of Equilibrium Resource Competition may be limited.